Electrolytic shaping apparatus



y 13, 1939 L. A. WILLIAMS 3,444,069

ELECTROLYTIC SHAPING APPARATUS Original Filed Nov. 10, 1958 Sheet of 5P0 WE? IN VEN TOR.

y 1969 L. A. WILLIAMS 3,444,069

ELECTROLYT I C SHAPING APPARATUS Original Filed Nov. 10, 1958 Sheet 3 ofs CONTEOA flMPt #751 INVENTOR.

094%! a WWW,

May 13, 1969 l L. A. WILLIAMS 3,444,069 v ELECTRQLYT I C SHAP INGAPPARATUS Original Filed Nov. 10, 1958 Sheet 31 of s IN V EN TOR.

0972/12 (Z '(c& 40-

Maia l n 3,444,069 ELECTROLYTIC SHAPING APPARATUS Lynn A. Williams,Winnetka, Ill., assignor to Anocut Engineering Company, Chicago, L, acorporation of Illinois Application Dec. 8, 1961, Ser. No. 158,042,which is a division of application Ser. No. 772,960, Nov. 10, 1958, nowPatent No. 3,058,895, dated Oct. 16, 1962. Divided and this applicationJuly 25, 1966, Ser. No. 567,556 Int. Cl. B23p N14 US. Cl. 204-224 ClaimsThis application is a division of my application Ser. No. 158,042, filedDec. 8, 1961, now US. Patent 3,276,987, entitled Electrolytic ShapingApparatus, which in turn is a division of my application Ser. No.772,960, filed Nov. 10, 1958, entitled Electrolytic Shaping, now issuedinto Patent No. 3,058,895, dated Oct. 16, 1962.

It has long been known that metal and metalloid materials may be removedby electrolytic attack in a configuration where the metal or metalloidworkpiece is the anode in an electrolytic cell. This principle has beenused industrially to some degree for the removal of defective platingand the like, and is sometimes referred to as stripping." It has alsobeen used to some extent for electrolytic polishing in whichapplication, however, the principal purpose is to produce a smoothfinish with a minimum removal of the work material. Here the purpose isto remove substantial amounts of metal rapidly and with accuracy.

In the present instance, the term metalloid is used somewhat speciallyin referring to those electrically conductive materials which act likemetals when connected as an anode in an electrolytic cell, and arecapable of being electrochemically eroded. The term as used here and inthe claims includes metals and such similarly acting materials astungsten carbide, for instance, and distinguished from such conductivenonmetalloids as carbon.

George F. Keeleric has proposed in his Patent No. 2,826,540, issued Mar.11, 1958, for Method and Apparatus for Electrolytic Cutting, Shaping andGrinding the use of electrolysis in conjunction with a metal bonded,abrasive bearing, moving electrode, and the method and apparatus of thisKeeleric patent have found extensive industrial use.

The present invention departs from the teachings of Keeleric inutilizing relatively fixed or slow moving electrodes without abrasive,and is intended for work of a quite different character, as will appearin the detailed description of the invention which follows.

In general, in the present invention an electrode, quite frequently ahollow electrode, is advanced into the work material by mechanical meanswhile electrolyte is pumped through the work gap between the electrodeand the work, and at times the hollow portion of the electrode, undersubstantial pressure. In some circumstances the side walls of theelectrode are protected by an insulating material so as to minimizeremoval of work material except where desired. Various forms ofelectrodes are used for different kinds of work, and likewise differenttechniques of advancing the electrode toward and into the work materialare used, depending upon the nature of the operation to be performed. Animportant aspect of the invention lies in providing electrodes in whicha flow of electrolyte between the electrode and the work is maintainedat high velocity and across a short path between the point of entry andthe area of exit regardless of the overall size of the electrode. Anelectric current is supplied so that current passes from the electrode,which is negative, through the electrolyte to the workpiece, which ispositive. For purposes of shaping the electrodes, direct current may bepassed in the opposite sense to make the electrode posiatent C tive. Insome instances, alternating current may be used.

Among the objects of the invention are the following:

To provide novel apparatus for rapid removal of work material byelectrolytic means;

To provide automatic means for advancing electrodes toward and into thework material;

To provide novel mechanism for accomplishing variable feed rates foradvancing electrodes toward and into work material for electrolyticremoval thereof.

Other objects and advantages will become apparent from the followingdescription taken in conjunction with the accompanying drawings, whereinFIG. 1 is a perspective view of one form of electrolytic shapingapparatus embodying the present invention;

FIG. 2 is a diagrammatic representation of an electrolytesupply systemwhich forms a portion of the apparatus of FIG. 1;

FIG. 3 is a diagrammatic representation of apparatus embodying thepresent invention, showing one control mechanism therefor including anarrangement for controlling the speed of advance of the electrode;

FIG. 4 is a circuit diagram of a portion of the control system of theapparatus of FIG. 3;

FIG. 5 is a diagrammatic representation of the apparatus of the generalcharacter of FIG. 3, but showing an alternative control arrangementtherefor; and

FIG. 6 is a diagram of a portion of the apparatus of FIG. 5.

Referring to FIG. 1, the apparatus of this invention includes a framemember 1 which in this instance is the frame member of a conventionaland well known arbor press sold under the trade name of Famco. Itincludes a base section 3, a column 5, and a head 7 which is adapted inthe conventional manner to accommodate a ram 9 for verticalreciprocating motion. The detail of the ram mounting is not important tothis invention, but it is desirable to provide adjustable gibs or theequivalent in the head so that the ram may move vertically with a smoothaction and without lateral play which might introduce undesired sidemotion. To the bottom end of the ram 9 there is mounted a workplate 11,made of an electrically insulating material which is resistant to thecorrosive effect of the electrolyte, and through which a plurality ofbolt holes is provided to permit adjustable mounting of a work holdingvise 15.

On the base portion 3 there is mounted a metal bottom plate and on topof this a waterproof chemical resistant plastic mounting plate 19. Thisis provided with a number of threaded bolt holes to permit mounting ofan electrode holder 21, which is made of suitable metal and is providedwith one or more mounting slots so that it can be adjusted as to itsposition by selection of the suitable bolt holes in mounting plate 19.

At the working end, the electrode support member 21 is hollow and isadapted to receive an electrolyte feed tube fitting 27 connected to aline leading to a source of electrolyte under pressure.

Extending from the upper surface there is mounted an electrode 31,having a conductive working face, shown here as fastened by brazing to apipe nipple threaded into the electrode support member 21. Within thehollow support member 21 the electrode is connected by a suitablepassage to the feed tube fitting 27. The electrode 31 may take anysuitable form, e.g., those shown in Patent No. 3,058,895.

An electric cable 34 is connected to the electrode block or supportmember 21 and supplies current from the power source. Another electriccable 35 is fastened to work plate 11 to furnish the other (normallypositive) connection from the power source.

To move the work plate 11 up and down, a lead screw 37 is secured to andextends upwardly from the upper end of the ram 9. A lead nut 39 isthreaded upon the lead screw and is mounted between two horizontalplates 41 which are supported by four column bars 43. The lead nutperipherally is formed as a worm gear so that it may be rotated to movethe lead screw 37 up and down. A journal plate 45 is mounted to theplates 41 and carries a bearing bushing 47 which supports the outboardend of a drive shaft 49 which carries worm Sll meshed with theperipheral worm gear of lead nut 39.

The worm drive shaft 49, is in turn, rotated by a variable speedelectric motor drive 53 mounted upon a platform 55 attached to thecolumn 5. This drive mechanism has a speed adjusting handle 57 and areversing handle 59, the latter having a neutral midposition as well asupdrive and downdrive positions.

The sizes and proportions of the drive parts are arranged to permitadjustment in the vertical speed of movement of the workplate 11 fromzero to one inch per minute. The motion must be smooth, not jerky, andaccordingly reasonable accuracy and freedom from excessive friction arean advantage in the moving drive parts. The lead screw 37 may beprotected against splatter and corrosion by a plastic enclosure 61wrapped around the column bars 43.

A conventional dial indicator 63 is shown as mounted to the head 7 ofcolumn and has its working tip extended downwardly against the uppersurface of workplate 11 so as to indicate relative movement as betweenthese elements.

The entire assembly is mounted in a pan 65 which has an outlet spudadapted to drain electrolyte back into-a supply sump or reservoir 74.The workplate 11 is fitted with plastic curtains 71 which can be tuckeddown below the level of the pan top to prevent excessive splatter, andto enclose the work area for the workpiece and the electrode 31.

The plumbing system (FIG. 2) comprises a low pressure pump 73 whichfeeds a suitable conductive electrolyte from the reservoir 74 through afilter 75 into high pressure pump 77, the outlet of which leads to abypass valve 79 which may be either manually set or of the spring loadedconstant pressure type. On the inlet side of the bypass valve 79 apressure gauge 81 is mounted. Also from the inlet side, a pipe lead istaken through,a needle valve 83 to an electrolyte feed tube 84 leadingto the electrode fitting 27. A second gauge 29 is connected to the feedtube 84 so as to indicate the pressure at the electrode.

In operation, a workpiece is positioned in the vise above the electrode31, and the workplate 11 is then driven down until the workpiece isalmost touching electrode 31 as gauged by a piece of paper or shim ofknown thickness, say .003 inch. The dial indicator 63 is then adjustedto zero minus the known thickness, .003 inch in this example. Thecurtains 71 are lowered or otherwise closed, the electrolyte pumps 73and 77 are started, and the valves 79 and 83 are adjusted so that gauge81 reads about 120 p.s.i., and gauge 29 about 90 p.s.i. This is donewhile the reversing handle 59 is in neutral position. Then,simultaneously, the reversing handle is moved to down drive position,and the electric power supply is turned on.

As the electrode approaches the workpiece, there will be a rise inpressure at the gauge 29. If the capacity of pumps 73 and 77 is severaltimes the free flow discharge rate through the electrode, the pressureupstream of the needle valve 83 and of bypass valve 79 as readat gauge81 will change scarcely at all with changes in proximity of theelectrode 31 to the work, for most of the flow is passing through bypassvalve 79, and it is the adjustment of this which is principallydeterminative of the pressure at gauge 81. In short, the pumps andpumping system up to needle valve 83 constitute a substantially constantpressure source. The same result may be obtained in many other ways. Aconstant pressure type pump may be used;

e.g., a centrifugal pump operating near cutoif. Or a pressure regulatormay be used. Or a spring loaded relief valve adapted to maintainconstant pressure may be used.

Needle valve 83, however, is set so as to constitute a sufiicientrestriction to flow so that when the electrode is discharging into theopen, the pressure, as read at gauge 29, will be noticeably lower thanwhen its outlet is restricted by being in close proximity to the work.

Thus, if gauge 81 normally reads 120 p.s.i., then when the electrode 31touches the workpiece so as to shut off the flow, or nearly so, thepressure downstream of needle valve 83, as read at gauge 29, will riseto almost the same value, 120 p.s.i. If, however, the electrode 31 isspaced away by several thousandths of an inch, the pressure at gauge 29will drop, say to p.s.i.

This change in liquid pressure may be used in adjusting the rate of feedof the work toward the electrode. The initial feed rate may be set at alow level (for an unknown working condition or work material), and thenincreased by adjustment of the handle 57. Gauge 29 is observed to watchfor a pressure rise which approaches that of gauge 81. It takes a littletime for the pressure reading to stabilize during actual removaloperations, for inasmuch as material is being removed by anodicdissolution, it is necessary for the moving electrode to catch up withthe receding work material and to establish an equilibrium spacingdistance, for as the electrode comes closer to the work, the removalrate tends to increase. By the exercise of reasonable care, it ispossible to make a precise adjustment such that the electrode pressuregauge 29 reads only a few pounds per square inch lower than gauge 81,indicating that the electrode is moving forward at such a rate as toleave only a small gap between the electrode and the work.

In effect, this hydraulic system constitutes a flow meter, and the sameresult may be obtained by using a more formal flow meter to sense theHow rate through the gap between the electrode and work. Such flowmeters may be of any suitable sort, as, for instance, of the orificetype (which, in effect, uses the principle of the system justdescribed), or of some other type, for example, that in which a movingbob is supported by upward flow in a conical glass vessel (e.g., theFischer & Porter type).

It is not easy to measure this gap with accuracy, as apparently it isnot always uniform at every point, but as measured in a practical way,by turning off the current and advancing the electrode until it seems tobottom, the distance may be as small as .001 inch or less, to as much as.010 inch, with satisfactory results, although it is preferred to workwith the shortest spacing distance which can be managed without causingoccasional contact and arcing between the electrode and the work, and Ihave found that about .002 inch to .005 inch is usually a safe distancewhile still permitting rapid removal of work material.

In general, low voltages and close spacing, of the order of .001 inch to.005 inch, give high removal rates and low electric power costs and ahigher degree of accuracy, but less striation is produced upon the sidewall of the work cavity when greater spacing, of the order of .010 inch,is used. The greater spacing results in a lower work removal rate unlessthe voltage is raised, however, since removal rate is a function ofcurrent. As a practical matter in most applications, I prefer to useabout 4 to 15 volts and from to 3000 amperes per square inch of activeelectrode area.

It should be noted that work material is removed by electrolytic action,not by spark or are erosion, as with the so-called electrodischargemethod. This is important for several reasons, among them the fact thatdamaging thermal metallurgical efiects on the work material are avoidedand that there is virtually no erosion of the electrode. The fact thatthe electrode is not eroded is of great importance where the cavity isto be accurately shaped, for accurate shaping is rendered very difficultwhen the electrode is being eaten away at a rate rapid enough to alterits dimensions during the operation.

Thus, it is important to avoid too fast a feed rate which may causearcing between the electrode and the work.

Another method of gauging the feed rate is by reference to an ammeter inthe electrolytic power supply circuit. Once the penetration of theelectrode into the work has been well established, the rate of feed isgradually increased until an arc is observed. Usually this will be ofshort duration. The reading of the ammeter is observed and read justprior to the first arc, and the' speed is then adjusted downwardly untilthe ammeter shows a reading of little below the critical point where thefirst arc occurred.

A transducer sensitive to either the electrolyte liquid flow rate or theelectrolytic electric current may be used as the signal generatingelement in an automatic feed control system.

FIG. 3 is a schematic illustration of one type of apparatus forautomatic control of the feed rate of the electrode. Motor 101 is of thedirect current shunt wound type, and serves to advance the electrode 31toward the work W (or the work W toward the electrode) by a screw drive,all in the general manner shown in FIG. 1, except that the speed ofmotor 101 is varied electrically and automatically rather than manually.Other suitable mechanical configurations will be self-suggesting.

The electric supply system and amplifier 103 include rectifier circuitsto provide a relatively fixed direct current voltage for the field ofmotor 101 and an automatically adjusted voltage for the armature so thatthe motor speed is automatically varied with a variation in armaturevoltage. The amplifier 103 derives a signal from a pressure responsivetransducer 105 (FIG. 4), arranged to respond to the pressuredifferential across the needle valve at 107 which is in the line betweenthe pump 108 and the electrode 31. As one example, a diaphragm device orother pressure responsive sensing element may be mounted so that theliquid pressure differential thereacross causes a variation in pressureupon a carbon pile variable resistor 109 connected in a bridge circuitas in FIG. 4. For this purpose, however, I prefer to use a variableimpedance, for example, a pressure actuated variable capacitor, in anoscillator circuit feeding the output to a discriminator to derive acontrol signal. As the value of the capacitor changes, it alters theoscillator frequency, and this affects the signal. All this isconventional and well known, and needs no detailed description.

The change in pressure is thus used to provide signals to the grid of avacuum tube amplifier which terminates in one circuit where I have usedin a pair of 807 power tubes. The output tubes may be fed withalternating current from a transformer split secondary, and they thusserve as rectifiers as well as amplifiers and provide a variable directcurrent supply to the motor armature. The amplifier circuit is soarranged that an increase in pressure differential across the transducerelement 105, which reflects an increase in the electrode to workspacing, causes an increase in power output, thus causing the motorspeed to increase, which in turn causes the electrode to catch to thereceding work face.

Accordingly, the system serves to maintain a feed rate which is held ata level to maintain constant liquid flow in the electrolyte feed line assensed by a constant differential pressure across adjustable orifice orvalve 107. This assures substantially constant spacing between theelectrode 31 and the work W. In some situations there will be a tendencyfor the circuit to hunt, and antihunting circuit techniques may berequired. Thus, the gain of the amplifier may be made adjustable as bythe knob 11 1; capacitance with a slow bleed and a resistance feed maybe connected across one of the grid circuits, etc. These techniques donot relate to the novelty of this invention and are, therefore, notdescribed in detail, for

riate variable impedance) in circuit with transducer element 109 in suchmanner as to vary the level at which signal response occurs. In FIG. 4,resistors 109 and 117 are balanced against each other in a simple bridgecircuit, and should be regarded as representative of any variableimpedance, whether resistive, capacitive, or inductive. The cam will beshaped to alter the feed rate as desired to produce the variations inwidth of cavity which are wanted. It should be understood that where thetransducer element 109 is not of the resistance type, then element 117need not be a resistor. If, for example, transducer is a variablecapacitor, then element 117 may be a vari able capacitor; or if 105 is avariable inductor.

The system just described constitutes a flow meter for a sensing andcontrol device in which the flow rate range may be set for the desiredresponse level, depending upon the area of the electrode. Other types offlow meters capable of providing an electrical control signal may beused; for example, a magnetic flow meter in which an AC magnetic fieldis impressed across a nonconductive section of electrolyte feed line andtwo electrodes set in a plane transverse to the field. The electrolyteacts as a moving conductor in the field, and its velocity determines thevoltage generated. The directly induced AC is canceled out electrically,and thus a signal is derived whose voltage is linearly proportional toflow rate.

The reversing switch at 11 9 enables the motor 101 to run in eitherdirection so as to extend or retract the electrode 31 as desired.

FIGS. 5 and 6 show an alternative arrangement to that of FIGS. 3 and 4.All parts are similar and bear like reference numerals except that theautomatic feed control is responsive to the electric current passingbetween the electrode 31 and the work W. Variation in the current inseries coil 121 affects the saturation of the iron core 123 which inturn is reflected in a change in inductance of coil 125. This mechanism,therefore, acts as a variable inductance which can be used to modulatethe output of the amplifier 103. When the electrolytic current risesabove a predetermined level, the voltage to the armature of motor 101 isreduced to slow the speed of advance.

Variable speed is accomplished by the same type of cam system used inthe apparatus of FIG. 3. One form of interconnecting bridge circuitrywhich may be housed principally within the amplifier box at 103 is shownin FIG. 6.

Variable inductor 125 responsive to current value is balanced againstvariable inductor 127 actuated by cam 113 in a circuit with fixedresistors 129 such that the level of amplifier response is varied inaccordance with the electrolytic current in the circuit and the positionof the electrode. Variable inductor 127 may be of any suitable type suchas a coil 131 having a movable core 133 attached to the follower of camplate 113.

From the foregoing it will be appreciated that the objectives which wereclaimed for this invention at the outset of the description are fullyattained by the apparatus described and shown.

Also, from the above description of my invention, it will be appreciatedthat many changes may be made in the apparatus without departing fromthe scope or spirit of the invention, and that the scope of theinvention is to be determined from the scope of the accompanying claims.

Iclaim:

1. In an apparatus for electrolytically shaping an electricallyconductive and electrochemically erodible workpiece, the combinationincluding, mounting means for the workpiece, an electrode having aconductive working face adapted to be brought into close spacingrelationship with the workpiece to define a work gap of predeterminednarrow spacing between the workpiece and said electrode working face,means connected for pumping an electrolyte to and through the work gap,electric circuit means connected for supplying an electrolyzing currentbetween the workpiece and said electrode working face, power meansconnected to said workpiece mounting means and to said electrode forpositively moving the workpiece and said electrode working facerelatively toward each other as material is removed from the workpiece,and control means for said power means for automatically adjusting therate of relative advance of the workpiece and said electrode workingface.

2. Apparatus as claimed in claim 1, wherein said control means issensitive to an operating variable in the apparatus.

3. Apparatus as claimed in claim 1, including actuating means beingsensitive to the rate of flow of the electrolyte to and through the workgap.

4. Apparatus as claimed in claim 3, including means sensitive to theposition of said electrode for additionally actuating said controlmeans.

5. Apparatus as claimed in claim 3, including means sensitive to anoperating variable other than the electrolyte flow rate for additionallyactuating said control means.

6. Apparatus as claimed in claim 1, including actuating means for saidcontrol means, said actuating means being sensitive to the electrolyzingcurrent in said electric circuit.

7. Apparatus as claimed in claim 1, including means sensitive to theposition of said electrode for additionally actuating said controlmeans.

8. Apparatus as claimed in claim 1, wherein said power means includes anelectric motor, and said control means includes an electric circuit forsaid motor to control the speed of the latter.

9. Apparatus as claimed in claim 8, wherein said electric circuitincludes an amplifier connected to sense the rate of electrolyte flow toand through the Work gap.

10: Apparatus as claimed in claim 8, wherein said electric controlcircuit includes an amplifier connected to sense the electrolyzingcurrent passing between the workpiece and said electrode working face.

References Cited UNITED STATES PATENTS 3,219,564 11/1965 Wilkinson204224 XR 3,228,863 1/1966 Wanttaja et a1. 204-224 XR 3,288,693 11/ 1966Livshits 204143 3,338,808 8/1967 Johnson 204-143 3,365,381 1/1968Fromson 204143 HOWARD S. WILLIAMS, Primary Examiner.

D. R. VALENTINE, Assistant Exmm'ner.

US. Cl. X.R. 204-143, 225

22x3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,444,069 D d May 13, 1969 Inventor( Lynn A. Williams It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 6, line 20, after "variable inductor" insert --,then element 117will be a variable inductor SIGNED AND SEALED SEP 2 1959 (SEAL) Attest:

Edward M'Flemhcr'h WILLIAM E. SCIHUYLER, JR- Attesting OfficerCommissioner of Pat n

1. IN AN APPARATUS FOR ELECTROLYTICALLY SHAPING AN ELECTRICALLYCONDUCTIVE AND ELECTROCHEMICALLY ERODIBLE WORKPIECE, THE COMBNATIONINCLUDING, MOUNTING MEANS FOR THE WORKPIECE, AN ELECTRODE HAVING ACONDUCTIVE WORKING FACE ADAPTED TO BE BROUGHT INTO CLOSE SPACINGRELATIONSHIP WITH THE WORKPIECE TO DEFINE A WORK GAP OF PREDETERMINEDNARROW SPACING BETWEEN THE WORKPIECE AND SAID ELECTRODE WORKING FACE,MEANS CONNECTED FOR PUMPING AN ELECTROLYTE TO AND THROUGH THE WORK GAP,ELECTRIC CIRCUIT MEANS CONNECTED FOR SUPPLYING AN ELECTROLYZING CURRENTBETWEEN THE WORKPIECE AND SAID ELECTRODE WORKING FACE, POWER MEANSCONNECTED TO SAID WORKPIECE MOUNTING MEANS AND TO SAID ELECTRODE FORPOSITIVELY MOVING THE WORKPIECE AND SAID ELECTRODE WORKING FACERELATIVELY TOWARD EACH OTHER AS MATERIAL IS REMOVED FROM THE WORKPIECE,AND CONTROL MEANS FOR SAID POWER MEANS FOR AUTOMATICALLY ADJUSTING THERATE OF RELATIVE ADVANCE OF THE WORKPIECE AND SAID ELECTRODE WORKINGFACE.